A prosthetic hip replacement system comprises a femoral component and an acetabular component. The femoral component includes a spherical head which covers or replaces the natural head of the femur. The acetabular components typically include a spherically generated cup which mounts in the acetabular cavity, and a spherically generated liner which mounts in the cup. The spherical head of the femoral component is pivotally engageable in the spherically generated liner of the acetabular component.
Surgery to implant an acetabular component of the prosthetic system requires the surgeon to enlarge and reshape the acetabular cavity in the ilium of the patient. The surgeon is then able to insert the prosthetic cup of the acetabular component into the enlarged and reshaped acetabular cavity.
The surgeon typically uses a prior art acetabular reamer to enlarge and reshape the acetabular cavity of the patient. A typical prior art acetabular reamer includes a reamer head which is a hollow cutting tool with a generally hemispherical front cutting wall, an opposed generally planar rear mounting wall and a hollow bone accumulation cavity therebetween. More particularly, such a prior art reamer head is formed to include a plurality of cutting edges on the hemispherical front cutting wall. These cutting edges are dimensioned to bite into and grate away the bone tissue of the ilium as the reamer head is simultaneous rotated and advanced into the acetabular cavity of the patient. The grated bone tissue accumulates inside the hollow bone accumulation cavity of the reamer head, and the surgeon may subsequently pack the accumulated bone tissue around the prosthetic components to promote bone ingrowth for ensuring a tight fit between the bone and the prosthetic components.
The planar rear mounting wall of such a prior art acetabular reamer includes a non-circular aperture extending centrally therethrough to enable access to the hollow bone accumulation cavity inside the prior art reamer head, and to enable rotatable driving of the reamer head.
The prior art reamer head is used with an elongated prior art reamer shaft having opposed front and rear ends. The rear end is configured and dimensioned for mounting in the chuck of a surgical drill. The front end of the prior art reamer shaft has a non-circular cross-section corresponding to the non-circular aperture in the rear mounting wall of the prior art reamer head. Thus, the reamer head can be frictionally engaged on the front end of the prior art reamer shaft, and may be rotatably driven by the prior art reamer shaft and the surgical drill to prepare the acetabular cavity.
The required detachability between the reamer head and the reamer shaft has been a disadvantage of the prior art acetabular reamer. In particular, the bone tissue of the patient will engage with and exert forces on the cutting edges of the reamer head. The magnitude of these forces may vary from patient to patient depending upon the characteristics of the bone being cut by the reamer head. The surgeon must overcome these forces to withdraw the reamer head from the acetabular cavity. However, the forces exerted by the bone tissue on the cutting edges of the reamer head often exceed the engagement forces between the prior art reamer shaft and the reamer head. In these situations, the reamer shaft will disengage from the reamer head when the surgeon pulls rearwardly on the surgical drill. The surgeon then must use a separate gripping and/or retraction tool to disengage the prior art reamer head from the bone tissue defining the acetabular cavity.
To avoid these problems, some prior art acetabular reamers have included cumbersome latch mechanisms that can be actuated by the surgeon to lock the head to the shaft, and that can be actuated again by the surgeon to enable disengagement of the head. This prior art acetabular reamer latch operation represents a substantial inconvenience to the surgeon.
In view of the above, it is an object of the subject invention to provide an improved acetabular reamer.
It is further an object of the subject invention to provide a reamer head which is securely lockable with the shaft of the acetabular reamer.
It is an additional object of the subject invention to provide a reamer head that is easily disengageable from a reamer shaft.
It is another object of the invention to provide an acetabular reamer with a head that automatically locks to the shaft and automatically unlocks from the shaft during normal usage of the reamer.